March 17--The state's major health insurance companies tried to calm concerns about a proposal to stabilize the state's insurance market Wednesday with a letter promising that a "reinsurance" bill would lower rates.

But Gov. Mark Dayton isn't buying the promises.

In a series of letters back to the insurers, Dayton on Thursday asked for firmer commitments.

"Your letter says that you 'intend to continue serving Minnesotans' but you do not explicitly state that you will continue to serve the state," Dayton wrote. "The letter also clarifies that the money for reinsurance will be used to pay medical bills but does not commit to actually bringing down premiums for consumers."

He asked the leaders of the HMOs to "provide consumers, the Legislature, and me with these public commitments as soon as possible."

"Minnesotans deserve to know that a program of this scale and cost will actually have the intended results of stabilizing the individual insurance market and improving its affordability for consumers," Dayton said.

Reinsurance would spend as much as $300 million per year to cover the cost of the most expensive patients in the state's individual health insurance market. That's the market that covers people who don't get health coverage through an employer or a government plan, and affects less than 5 percent of the state.

Because the individual market has a high proportion of sick members, insurers have faced high medical costs that they've passed on to the whole market in the form of higher premiums. The state's experts predict reinsurance, by covering some of those high costs, could lead to premiums being 21 percent or more lower in 2018 than they would be without reinsurance.

Dayton sent letters to the CEOs of Blue Cross Blue Shield Minnesota, HealthPartners, Medica, UCare and PreferredOne. The separate letters were otherwise identical.